CARDIOVASCULAR SYSTEM LABORATORY

Heart (slide #80)
Place slide on white sheet of paper for orientation. Note:

On your scope start with LV. Note:

Now look at upper LA. Endocardium is much thicker than in LV. Myocardium is present.

Between LA and LV is large epicardial fat pad containing coronary vessels.

Elastic Arteries (slide #81 and #96)
#81 is H&E stain. Look at large circular aorta. Thin endothelial cell lining (t. intima)

T. media is concentric layers of smooth muscle separated by thinner wavy elastic lamellae. These darker pink bands really stand out if you lower your scope's condenser.

T. adventitia is lighter pink and contains abundant vessels (vasa vasorum)

#96 is Verhoff-vanGiesen stain for elastin so lamellae in t. media stain dark. Shows good differiention between t. intima and t. media and between t. media and t.adventitia.

Muscular arteries (slide #9,40,32)
#9 is sole of foot. Look deep in dermis to find large muscular artery. Landmark is prominent internal elastic lamina separating t. intima from t. media smooth muscle cells. May be wavy due to shrinkage during fixation, sometimes not but lower condenser as before to make it stand out. May look a little brownish pink. Veins and arteries often travel together. Artery always has more muscular t. intima, internal elastic lamina and usually is less "squashed" than its neighboring vein.

Also look in connective tissue in structures like the submandibular gland (slide 2 #40).

Slide #32 (small intestine) has many good profiles of arteries, veins, arterioles and venules. Since arteries often travel with their companion veins, differences in their structures can be compared. Why do you think small intestine is so densely vascularized? You'll know for sure after Dr. Eigenbrodt's lecture on the G.I. system later in the semester.

Arterioles
Look in above slides for small round, "muscular" vessels. Usually have one to two distinct layers of smooth muscle nuclei in t. media.

Large Veins (slide #81 and 96 again)
Collapsed profile next to aorta is vena cava. Note:

Medium veins
Look for these paired with muscular arteries (as in slide #9, and 32). T. media is much thinner than artery. In veins t. adventitia is usually the thickest layer. Watch for valves in veins. If you find one, share with your neighbor. These guys are sometimes hard to find.

Venules
Smallest vessels, if paired near an arteriole, venules will be less muscular having only the endothelial t. intima surrounded by some connective tissue. Good ones in tissue around small intestine (slide #32).

Capillaries (slide #9,23, 42, 54, 80, 89)
Obviously the "bridge" between the arteriolar and venous systems. Look in all slides for the smallest diameter vessel with an RBC in it. Since its wall is only endothelial cell small capillary will look like a class ring when viewed in cross section.

Continuous: Look in myocardium in slide #80 and in #23 just beneath the epidermal cell layers.

Fenestrated (with diaphragms): Obviously you can't see fenestrae (with or without diaphragms) at the LM level but look at small capillaries near thyroid follicles in #54.

Fenestrated (without diaphragms): Capillary loops in renal glomeruli in cortical regions on slide #89

Sinusoidal: Sinusoids contain RBC and run between hepatocyte "plates" in slide #42 of the liver. Note occasional flattened endothelial cell nuclei.

Lymphatics (#31, 81,96)
Hard to positively identify as look like veins but walls always much thinner. Never have RBC but may contain eosinophilic lymph and leukocytes. Look at central region of intestinal villi in intestine (slide #31). After a fatty meal these lymphatics swell and are termed "lacteals".

Thoracic duct (smallest structure on slide # 81 and #96) is main lymphatic drain back into systemic circulation. Note prominent t. media and vasa vasorum in t. adventia.